#1 - If it's just a post in the bounty thread, it is of little consequence to the forum. No one cares about those reporting posts as they are confined to the bounty thread.
#2 - I'm guessing this has something to do with Bounties again. So in the grand scheme of things doesn't matter to the average forum user.
Not going to lie when it comes to bounties, the only thing I care about is that it isn't for some scam ICO. These users are generally just fouling up twitter and Facebook. My only issue is when these users decide to go one further and start wearing a SIG and spewing low quality garbage everywhere.
3. What happens when a user have up to 500 activities but no merit as he is stocked in Jr. Memeber? Do you consider this encouraging? Because I understand irrelevant post are always deleted by the moderators of the various sections and for someone to have up to 500 activities, it means all the posts are not irrelevants.
This user would be a prime example of the system working. Anyone who can get 500 activity without a single merit, deserves to be stuck at Jr. Member level.
Not all irrelevant posts are deleted by moderators, most of the time they need to be reported before they get dealt with. Even then there is a line between being deserving of moderation and contributing in some way to the conversation. Not every post that isn't deleted or deemed relevant is deserving of merit, it still has to bring something extra to the conversation in some way.
#4 Is simple, merit is not moderated by the forum. Some DT may be tagging merit abusers in an attempt to keep the system functioning as intended. Others are documenting cases in the reputation thread for gross abuse, as for a while it was tied into the account hacks going on. The nice thing about that is that DT can tag people based on their personal preference, such as people begging for merit. The problem with merit abuse is there are guidelines for giving it out but it is up to peoples personal preference; so it's not always a clear case.